Method for aligning and handling fuel rods within a nuclear fuel bundle

ABSTRACT

A method of aligning a nuclear fuel bundle and handling selected fuel rods within the fuel bundle located in a spent fuel pool of a nuclear power plant. The bundle includes water rods, full-length and part-length fuel rods extending through a plurality of fuel spacers provided between top and bottom ends of the bundle, each spacer having a plurality of cells accommodating corresponding fuel and water rods. The method includes insertion of a rod grapple tool into a top end of a fuel bundle and down to a desired location within the bundle. A guide pin retrieval tool inserts into a side of the fuel bundle to remove a guide pin from a distal end of a gripper of the rod grapple tool, allowing the guide pin retrieval tool to grip a part-length fuel rod within the fuel bundle.

BACKGROUND OF THE INVENTION

This application is a divisional of U.S. patent application Ser. No.12/786,879, filed on May 25, 2010 now U.S. Pat. No. 8,050,378, which isa divisional of U.S. patent application Ser. No. 11/711,614, filed onFeb. 28, 2007 now U.S. Pat. No. 7,773,717, the contents of both of whichare incorporated by reference in their entirety.

FIELD OF THE INVENTION

Example embodiment(s) are related in general to systems for aligning andhandling fuel rods and water rods within a nuclear fuel bundle.

DESCRIPTION OF THE RELATED ART

A reactor core of a nuclear reactor plant such as boiling water reactor(BWR) or pressurized water reactor (PWR) has several hundred individualfuel bundles of fuel rods (BWR) or groups of fuel rods (PWR). During aplanned plant outage for the BWR, selected irradiated fuel bundles areremoved from the reactor core at the nuclear power plant and placed in aspent fuel pool for inspection and possible reconstitution of the bundleand/or maintenance. For example, there may be leaking fuel bundle whichnecessitates removing the irradiated fuel bundle from the core, as it isdesirable to service these bundles in the event of a broken fuel rodand/or damaged fuel spacer grid which may be causing the leak.Additionally, when the fuel bundle is removed from the core and placedin the spent fuel pool, it is desirable to manipulate the fuel bundlefor inspection purposes in order to search for additional possiblesources of damage or leaks, and/or to rotate the bundle for generalmaintenance and measurement.

A typical fuel bundle for a BWR includes a plurality of fuel rods andcentrally located water rods attached between an upper tie plate and alower tie plate. For example, in FIG. 24A, there is shown a fuel bundle15 for a BWR which includes a plurality of fuel rods 25 and one or morewater rods (water rods obscured and which may or may not be centrallylocated within bundle 15), connected between an upper tie plate 30 and alower tie plate 40.

FIG. 24B shows the same fuel bundle 15 as it would look upon removalfrom the core and prior to removal of the channel 20 for inspection andmaintenance. The bundle 15 includes a generally rectangular channel 20which extends the length of fuel bundle 15 and surrounds the fuel rods,water rods and upper and lower tie plates 30, 40. The channel 20 is anextruded alloy which encases the bundle 15. The fuel bundle 15 istypically delivered into the spent fuel pool via a fuel handling bridge(not shown) which is permanent machinery in reactor plants. The fuelhandling bridge attaches to the upper tie plate bail (handle) 35 of thefuel bundle 15 to move the fuel bundle 15 from the core to the spentfuel pool.

Typically the fuel bundle 15 shown in FIG. 24B is centered over a fuelprep machine (FPM-not shown), and a carriage of the FPM is raised toreceive the fuel bundle 15. As is well known in the art, the FPM isattached to a wall of the spent fuel pool in a nuclear power plant. Oncethe channeled fueled bundle 15 is place within the FPM, the channel 20and upper tie plate 30 are removed to expose the fuel rods 25 and thefuel bundle 15 upper end for inspection and/or maintenance purposes.

Of note, with continued power operations of the reactor core with theirradiated fuel bundle 15, the fuel bundle 15 can be subjected to bow ortwist. Twist/bow is caused by the amount of time the fuel bundle 15 hasbeen in-service. In other words, the more the bundle 15 is used in anoperating reactor core (i.e., the greater the exposure of the bundle inmegawatt-days per short time (MWD/st), the greater the twist/bowpotential. Accordingly, if the bundle 15 in the FPM exhibits twist orbow, it becomes substantially more difficult to remove selected fuelrods 25 in order to service/inspect the fuel bundle 15.

A fuel bundle exhibits twist and bow due to the growth of individualfuel rods over time and exposure within the core. In an example, a fuelbundle for a BWR is typically held together with a plurality of tierods. The lower end plugs of the fuel rod screw into the lower tie plate40, and the upper tie plate 30 slides in place over the fuel rods 25,water rods and tie rods. The upper end plug of the tie rods are threadedand receive nuts which secures the fuel bundle 15 together.

As the fuel rods 25 grow due to irradiation, the fuel rods 25 havelittle room to expand as they are sandwiched between the upper tie plate(UTP) 30 and lower tie plate (LTP) 40. The fuel rods do not all growexactly the same amount, resulting in an uneven growth; this causesportions of the fuel bundle 15 to lengthen more than other areas withinthe bundle 15, producing what's known as bow and twist.

Most fuel bundle designs in BWRs (such as the fuel bundle 15) and PWRsinclude a plurality of fuel spacers 80, also referred to as spacergrids, which are axially spaced along the length of the fuel bundle 15.A typical fuel spacer 80 or spacer grid includes a plurality of cells oropenings which accommodate the fuel rods and water rods there through.These fuel spacers 80 are generally not robust in construction, and canbe damaged during routine in-service fuel inspections while removing andinstalling full and part-length fuel rods and water rods in the bundlewithin the spent fuel pool. The damage caused to the fuel spacers 80could go unnoticed, and could cause additional damage to individual fuelrods 25 if a reconstituted fuel bundle (such as fuel bundle 15) isreturned to power operations within the core. Accordingly, duringremoval and installation of the fuel rods 25 in a given irradiated fuelbundle 15 within the spent fuel pool, there is a substantial probabilityfor fuel bundle component damage, either to the fuel rod itself, thespacers, the water rods or end plugs of fuel rods, which can occurduring the in-service maintenance of the fuel rods within the spent fuelpool.

Further, as the removed fuel bundle 15 within the spent fuel pool iscompletely submerged, most inspections are done remotely and maintenanceor repair is done by operators standing well above the fuel bundle 15,while utilizing a remote camera system and length handling poles withimplements at ends thereon. The handling poles are inserted down throughthe fuel bundle 15 to remove/install selected fuel rods.

With the upper tie plate 30, the channel clip (not shown) and thechannel 20 removed, workers typically utilize up to a 30-foot handlingpole to perform maintenance, installation and/or removal of fuel rods25. Particularly in the case of part-length fuel rods, which in somecase are substantially shorter than full-length fuel rods, only theskill and experience of the handler of the handling pole ensures that apart-length rod can be safely extracted (or installed) without causingdamage to the fuel spacers 80 or adjacent fuel rods 25. This is trueeven with the use of remote cameras positioned down in the spent fuelpool for monitoring the maintenance procedure.

Accordingly, conventional procedures for retrieving/installing apart-length fuel rod are time consuming if not impossible, cumbersomeand must rely on the experience and skill of the operator manipulatingthe handling pole to avoid damaging a fuel spacer 80 or adjacent fuelrod 25. As fuel bundle designs are becoming even more complex, thisinadvertent damage to the fuel spacers 80 and/or fuel rods 25 is evenmore likely without an adequate alignment and handling system.

BRIEF DESCRIPTION OF THE INVENTION

An example embodiment is directed to a system in a nuclear power plantfor aligning a nuclear fuel bundle and handling selected fuel rodsand/or water rods within the fuel bundle, where the fuel bundle residesin a spent fuel pool within the plant. The fuel bundle includes one ormore water rods and a plurality of fuel rods including full-length fuelrods and part-length fuel rods extending vertically within the bundlethrough a plurality of axially spaced fuel spacers provided between atop end and bottom end of the fuel bundle, each fuel spacer including aplurality of individual cells accommodating corresponding fuel rods andwater rods. The system includes a fuel prep machine (FPM) in the spentfuel pool for supporting the fuel bundle thereon, a bundle alignmentassembly attached to the fuel prep machine for aligning fuel rods withinthe fuel bundle to remove any twist or bow within the fuel bundle, a rodgrapple tool to extract selected part-length rods from the fuel bundle,and a fuel rod guide block slidable onto the top end of the fuel bundlefor protecting an uppermost fuel spacer of the fuel bundle and aligningfuel rods within individual cells of all the fuel spacers in the fuelbundle.

Another example embodiment is directed to a system of a reactor plantfor removing bow and twist within a nuclear fuel bundle to permitinspection and replacement of one or more fuel rods or water rods withinthe fuel bundle, where the fuel bundle has been removed from a reactorcore to a spent fuel pool within the plant. The system includes a fuelprep machine (FPM) in the spent fuel pool for supporting the fuel bundlethereon, and a bundle alignment system attached to the fuel prep machinefor aligning fuel rods within the fuel bundle to remove any bow or twistwithin the fuel bundle.

Another example embodiment is directed to a fuel rod alignment systemfor a fuel bundle residing in a spent fuel pool within the plant. Thefuel bundle includes one or more water rods and a plurality of fuel rodsincluding full-length rods and part-length rods extending verticallywithin the bundle through a plurality of axially spaced fuel spacersprovided between a top end and a bottom end of the fuel bundle, eachfuel spacer including a plurality of individual cells accommodatingcorresponding fuel rods and water rods. The system includes a fuel prepmachine in the spent fuel pool for supporting the fuel bundle thereon,and a fuel rod guide block slidable onto the top end of the fuel bundlefor protecting an uppermost fuel spacer of the fuel bundle and aligningfuel rods within individual cells of all the fuel spacers in the fuelbundle.

Another example embodiment is directed to a system for removing apart-length fuel rod from a fuel bundle, where the fuel bundle residesin a spent fuel pool of a nuclear reactor plant. The system includes afuel prep machine in the spent fuel pool for supporting the fuel bundlethereon, and a rod grapple tool having a first end handled by anoperator above the fuel pool in the plant and a second end inserted at atop end of the fuel bundle on the fuel prep machine to retrieve thepart-length fuel rod within the bundle. The second end has a protective,removable guide pin which prevents the rod grapple tool from damagingthe fuel bundle as the rod grapple tool is inserted into the bundle. Thesystem includes a guide pin retrieval tool for, when the rod grappletool has been inserted into the fuel bundle so that the guide pin andgripper are in position over the part-length fuel rod to be extracted,removing the guide pin to permit the gripper of the rod grapple tool tobe attached to an upper end plug of the part-length fuel rod to extractthe part-length fuel rod from the bundle.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will become more apparentby describing, in detail, example embodiments thereof with reference tothe attached drawings, wherein like elements are represented by likereference numerals, which are given by way of illustration only and thusdo not limit the example embodiments of the present invention.

FIG. 1 is a side view of a system 1000 for aligning and handlingselected fuel rods 155/160 and/or water rods 170 within a fuel bundle,in accordance with an example embodiment.

FIG. 2A is a perspective view of a fuel prep machine (FPM) 110 forsupporting an irradiated fuel bundle 150, showing the channel 20 removedin a spent fuel pool of a nuclear power plant.

FIG. 2B is a partial enlarged view of FIG. 2A to illustrate a carriage120 of a fuel prep machine (FPM) 110 in further detail.

FIG. 2C is a perspective view of the fuel prep machine (FPM) 110supporting the fuel bundle 150 thereon, with the channel 20 alreadyremoved.

FIG. 3A is a front view of a bundle alignment assembly 200 in accordancewith an example embodiment.

FIG. 3B is a side view of FIG. 3A, the bundle alignment assembly 200.

FIG. 3C is an enlargement of detail A in FIG. 3B, detailing part of thebundle alignment assembly 200.

FIG. 4 is a partial side view of system 1000 in the vicinity of thelower rotating fixture 124 in order to show the connection of the bundlealignment assembly 200 to the fuel prep machine's (FPM) carriage 120.

FIGS. 5 and 6 are partial perspective views of the system 1000 to showthe attachment of an upper mount block 208, and a lower mount attachmentblock 218 of the bundle alignment assembly 200 to the upper rotatingfixture 122 of the carriage 120.

FIG. 7A is a perspective view of an alignment station 210 showingalignment blade bundles 220 in a neutral or disengaged position.

FIG. 7B is a perspective view of the alignment station 210 showingalignment blade bundles 220 in an engaged position.

FIG. 7C is a top view of the alignment station 210 with the alignmentblade bundles 220 in an engaged position to illustrate a grid 230created for alignment of fuel rods 155, 160 and the water rods 170within the fuel bundle 150.

FIG. 8A is a perspective view of the alignment blade bundle 220 inaccordance with an example embodiment.

FIG. 8B is an exploded view of FIG. 8A illustrating the constituentparts of the alignment blade bundle 220.

FIG. 9 is a partial perspective view of the system 1000 illustrating arod guide block 300 lowered over a fuel bundle 150 in accordance with anexample embodiment.

FIG. 10 is an exploded view of the fuel rod guide block 300 toillustrate constituent parts in more detail.

FIGS. 11A and 11B are partial cutaway views of the fuel rod guide blockto illustrate the placement of the fuel rod guide block 300 within thefuel bundle and above the top of the uppermost space 180A.

FIG. 12 illustrates a partial perspective view of the system 1000 withthe fuel rod guide block 300 in place on the fuel bundle 150.

FIG. 13 illustrates a portion of a rod grapple tool 400 as beinginserted into a fuel bundle 150, until it reaches a position just abovethe upper end plug 165 of a part-length rod 160.

FIGS. 14A through 14D illustrate constituent parts of the rod grappletool 400 in more detail.

FIGS. 15A and 15B illustrate a fully extended lower position of the rodgrapple tool 400.

FIGS. 16A and 16B illustrate a fully closed position of the rod grappletool 400.

FIG. 17A is a perspective view of a handling pole 502 attached to therod guide pin retrieval tool 500.

FIG. 17B is an enlarged view of detail A in FIG. 17A showing the rodguide pin retrieval tool 500 lower portion in greater detail.

FIG. 18 illustrates different tongues 506 of various lengthconfigurations attachable to the end of the rod guide pin retrieval tool500.

FIGS. 19-22 illustrate a process for removing the guide pin 435 from therod grapple tool 400 within fuel bundle 150.

FIGS. 23A and 23B is illustrating the procedure for attaching thegripper 432 of rod grapple tool 400 to an upper end plug 165 of apart-length rod 160 within the fuel bundle 150.

FIGS. 24A and 24B illustrates a conventional Boiling Water Reactor (BWR)fuel bundle 15 with its channel 20 removed, and with its channel 20 inplace on the fuel bundle 150.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

As will be described in more detail below, an example embodiment isdirected to a system for aligning and handling selected fuel rods withina fuel bundle of a nuclear reactor which facilitates the ability ofhandlers to remove and install fuel rods without damaging the fuelspacers or adjacent fuel rods. The example system may provide astraight-line path to facilitate the extraction of fuel rods includingpart-length fuel rods without merely relying on the skill of the handlerto insure that the fuel rod is removed without damaging adjacent fuelrods or fuel spacers. The example system may thus enable the fuel rods,spacers or spacer grids, water rods and end plugs to be protected duringmaintenance and/or inspection procedures within the spent fuel pool.

FIG. 1 is a side view of a system 1000 for aligning and handlingselected fuel rods within a fuel bundle in accordance with an exampleembodiment. In FIG. 1, the fuel bundle 150 is supported by a fuel prepmachine (FPM) 110. The FPM 110 is attached to a wall 105 of a spent fuelpool 103 within a nuclear reactor. The fuel bundle 150 is shown with itsupper tie plate 30 and channel 20 removed, as this procedure is doneonce the fuel bundle 150 is lowered into the fuel prep machine 110. Inthis example, the fuel bundle 150 is for a BWR and has a 10×10 fuel rodmatrix (10 rows by 10 columns of full-length and partial-length fullrods), with a pair of centrally located circular water rods 170.However, fuel bundle 150 can have a configuration other than a 10×10fuel rod matrix (9×9, 12×12, etc.), and a different number of water rodsof different shapes and sizes, that may or may not be centrally locatedwithin the fuel bundle.

System 1000 includes a bundle alignment assembly 200 attachable to thefuel prep machine 110. The bundle alignment assembly 200 is provided foraligning fuel rods and water rods within the fuel bundle 150 to removeany twist or bow within the fuel bundle 150 and to provide astraight-line path for fuel rod installation and/or removal.

As will be seen in more detail below, the bundle alignment assembly 200includes a series of alignment stations 210. Each alignment station 210includes a plurality of rotatable pre-formed stainless steel blades andrigid stainless steel blades. In general, the bundle alignment assembly200 is lowered into position onto the fuel prep machine 110 and held inplace by mechanical means. The fuel bundle 150 is then placed into thefuel prep machine (FPM) 110 for inspection. When manually actuating thebundle alignment assembly 200 by means of a handling pole, the rotatablepre-formed stainless steel blades and the rigid stainless steel bladesare rotated together into the fuel bundle 150, creating a protectivegrid above each fuel spacer 180 while also capturing each individualfuel rod in the forward half of the nuclear fuel bundle 150.

One possible result of using the bundle alignment assembly 200 is toensure that an in-service (i.e., irradiated) nuclear fuel bundle such asfuel bundle 150 has any twist and/or bow removed there from, a conditionnormally caused by the harsh environment within reactor vessels. Theassembly 200 thus may provide a straight path for the removal andinstallation of individual fuel rods or water rods, while protecting thefuel spacers 180 from damage.

System 1000 further includes fuel rod guide block 300 slidable onto thetop end of the fuel bundle 150 for protecting an uppermost spacer fromdamage, shown as spacer 180A in FIG. 1. The fuel rod guide block 300protects the uppermost spacer 180A of the fuel bundle 150 from damagewhile inserting fuel rods by physically protecting the upper side of thespacer 180A. The fuel rod guide block 300 also enables aligning of fuelrods within individual cells of all the fuel spacers 180 in the fuelbundle 150.

Additionally, the fuel rod guide block 300 provides a lead-in toinitially start a fuel rod into the fuel bundle 150 with desired properalignment. Further, the rod guide block 300 provides an obvious visualindication as to where a fuel rod needs to be inserted into the fuelbundle 150. This can enable less experienced handlers to perform fuelrod removal and insert procedures without requiring the skill of andexperience of the seasoned handler, since the fuel rod guide block 300helps to properly align each of the fuel rods of the fuel bundle 150 inthe vertical direction.

As will be shown in further detail hereafter in FIG. 10, the fuel rodguide block 300 includes two horizontally-oriented, spaced (upper andlower) stainless steel plates separated by a plurality ofvertically-arranged stainless steel tubes. Each of the plates has aplurality of openings which align with the locations of the fuel rodsand water rods within the bundle 150. The fuel rod guide block 300 isheld together by two vertically-oriented side plates attached bysuitable fasteners to each of the upper and lower plate. A bail (handle)with restricted movement is attached to the fuel rod guide block 300 forthe purpose of lowering it onto the fuel bundle 150 that is supported onthe FPM 110, prior to in-service fuel inspections.

Thus, the fuel rod guide block 300 is designed to slide onto the top ofthe nuclear fuel bundle 150 positioned in the FPM 110. As will bedescribed in further detail below (FIGS. 11A and 11B), once installed,the fuel rod guide block 300 is limited to its downward travel intobundle 150 by creating a restricted fit between the water rods andtapered central openings in the upper plate of the fuel rod guide block300 which are aligned with the water rods. The fuel rod guide block 300comes to rest onto tapered sections of a water rod transition area.

Although system 1000 is shown with both the bundle alignment assembly200 and rod guide block 300 included, each can be used independentlywithout the other for inspection and/or maintenance of an irradiatedfuel bundle 150. In an example, fuel bundle 150 can be an irradiatedfuel bundle that has been removed from the BWR core, a previously usedbundle 150 that is stored within the spent fuel pool of the plant, a newfuel bundle 150 that has been stored within the spent fuel pool of theplant while awaiting placement within the reactor's core as a reload, afuel bundle having been removed from an on-site new fuel storage faultfor placement in the fuel pool, and/or a fuel bundle from a fixed ormovable dry storage cask for placement into the fuel pool).

In another example embodiment, the FPM 110 and only bundle alignmentassembly 200 are used together for supporting a fuel bundle 150 andaligning the fuel rods and water rods of the bundle for inspectionand/or rod replacement purposes. For any irradiated bundle 150exhibiting twist and or bow, the FPM 110 and bundle alignment assembly200 may thus constitute a system for removing the twist/bow within afuel bundle to permit inspection and possible replacement of one or morefuel rods or water rods therein within the spent fuel pool of the plant.In this alternative embodiment, the rod guide block 300 may notnecessarily be installed.

In the event that an irradiated fuel bundle 150 exhibits no twist orbow, the bundle alignment assembly 200 does not need to be installed,only the rod guide block 300 is installed on the top of the bundle 150above the uppermost spacer 180A. In this alternative embodiment, the rodguide block 300 with FPM 110 can represent a separate fuel bundlehandling system, in which the FPM 110 supports fuel bundle 150 thereonand the rod guide block 300, when installed on the top end of the bundle150, aligns each of the fuel rods 155 and water rods 170 of the fuelbundle 150 in the vertical direction.

Referring again to FIG. 1, the system 1000 also includes a rod grappletool 400. In particular, rod grapple tool 400 is utilized by a handlerfor the removal of fuel rods, such as certain tie rods and/or theshorter part-length fuel rods which are deeper within the fuel bundle150. A different, pre-existing rod grapple tool may be used for theremoval and/or reinsertion of standard full length fuel rods and certaintie rods, as the upper end plugs of the standard full length fuel rodsand tie rods may be designed differently than that of the upper end plugof the part-length fuel rod. The rod grapple tool 400 is designed so asto mimic the dimensions of individual fuel rods. This allows the rodgrapple tool 400 to safely pass through the fuel spacers 180 withoutcausing component damage.

As will be seen in more detail below (FIG. 15B, for example), the rodgrapple tool 400 includes a gripper (also referred to as a rod grapple)at the end of the tool 400 that is inserted into the fuel bundle 150 forextracting a part-length fuel rod. For insertion of the rod grapple tool400 into the bundle 150, the rod grapple tool 400 includes a removableguide pin (shown in more detail in FIGS. 15A and 15B). The guide pin isinserted into the gripper and is generally tapered to a rounded pin end.Since the gripper has a blunt end, the guide pin is provided to preventdamage to the fuel spacers 180 as the rod grapple tool 400 is insertedinto the fuel bundle 150.

Once the rod grapple tool 400 has been fitted with the guide pin,inserted into the fuel bundle 150 and positioned at a given axiallocation within the fuel bundle 150 above a part-length fuel rod to beextracted, a pin retrieval tool 500 is utilized to remove the guide pinfrom the end of the grapple tool 400. The pin retrieval tool 500 isshown in more detail hereafter and is attached at the end of a separatehandling pole 502 for insertion down into the fuel pool to retrieve theguide pin from the rod grapple tool 400 end.

Accordingly, the rod grapple tool 400 and pin retrieval tool 500 maycomprise a separate system for removing a part-length rod from a fuelbundle, independent of the bundle alignment assembly 200 and rod guideblock 300 of the system shown in FIG. 1. Further, the rod guide block300, rod grapple tool 400 and guide pin retrieval tool may comprise aseparate system for removing part-length rods for the fuel bundle 150,independent of the bundle alignment assembly 200.

In general to remove a part-length rod from fuel bundle 150, thetapered, rounded guide pin is inserted in the end of the gripper so thatonly the tapered end of the guide pin extends from a lower housing ofthe rod grapple tool 400. The gripper is designed to be attached to anupper end plug of a part-length fuel rod for rod extraction. Onceattached, the gripper is retracted into the lower housing so that thelower housing of tool mates with a shoulder of the end plug at the topof the part-length rod, providing a smooth continuous surface betweenthe part-length rod and the attached rod grapple tool 400.

The guide pin thus creates a lead-in for the rod grapple tool 400 topass through each fuel spacer 180. Once the rod grapple tool 400 is inposition above a selected part-length fuel rod, the guide pin is removedusing the pin retrieval tool 500 so that the gripper of tool 400 can beinserted over the partial length rod's end plug and engaged for fuel rodextraction.

As to be described in more detail below (FIGS. 17A and 17B), the pinretrieval tool 500 includes a tongue with a mating bore that receives amating portion of the guide pin. The pin retrieval tool 500 is fixed tothe end of the handling pole 502 to allow for remote handling of theguide pin within the fuel bundle 150. The pin retrieval tool 500 thusprovides a positive means of capturing the guide pin 435 for repetitiveuse.

FIGS. 2A through 2C illustrate an example fuel prep machine 110 used insystem 1000 in accordance with an example embodiment. Many nuclear powerplants employ fuel prep machines 110 in the spent fuel pool of the plantto support an irradiated fuel bundle 150, thus a detailed explanation isomitted for purposes of clarity. As shown in FIGS. 2A to 2C, the fuelprep machine (FPM) 110 generally includes a stanchion 114 extending froman FPM platform 115 down into the spent fuel pool of the plant. The FPM110 includes a carriage 120 which slides up and down as needed on rails116 formed on the stanchion 114. The carriage 120 includes an upperrotating fixture 122 and a lower rotating fixture 124 which permitrotational movement of the fuel bundle 150 therein.

The FPM 110 is a permanent fixture in the spent fuel pool 103 and ismounted on one of the walls 105 of the spent fuel pool 103, as is known.The FPM platform 115 is the only portion of the FPM 110 that is abovewater and includes a safety handrail 117. A fuel bundle (such as bundle150) is delivered to the FPM 110 via a fuel handling bridge (not shown,this is a permanent fixture in a reactor plant). Once in place over thecarriage 120, the carriage 120 is raised to receive the fuel bundle 150.The fuel bundle 150 may be rotated in either direction up to 360 degreesas desired for inspection and/or maintenance purposes via upper andlower rotating fixtures 122, 124.

FIG. 3A is a front view of the bundle alignment assembly 200 and FIG. 3Bis a side view of assembly 200. FIG. 3C is an enlargement of detail A inFIG. 3B. Referring to FIGS. 3A and 3B, assembly 200 includes a pluralityof axially-spaced alignment stations 210 mounted to a mounting frame 205which is attached to the upper and lower rotating fixtures 122, 124 ofthe fuel prep carriage 120 on the FPM 110 as will be shown hereafter.The assembly 200 includes a bail 202 which enables it to be lowered ontoand removed from the FPM 110. Each alignment station 210 includes asupport plate 206 with a plurality of alignment blade bundles 220mounted thereon. As best shown in FIG. 3C, the support plate 206 ismounted to a cross member 204 affixed to the mounting frame 205 and alsoto the mounting frame 205 by mechanical fastening means 214 (such asnut-screw-washer assemblies). Each alignment station 210 includes aplurality of alignment blade bundles 220 mounted thereon. In FIG. 3A,these are shown as blade bundles 220A, 220B and 220C.

As will be seen in further detail below, the alignment blades of thesebundles are rotated to align fuel rods and water rods in the front halfof the fuel bundle 150 (due to clearance constraints of the FPM 110,half the bundle 150 is aligned at a time for inspection and/or rodremoval/installation in that half), then the bundle 150 is rotated toinspect and/or service the other half of the same bundle.

FIG. 4 is a partial side view of system 1000 in the vicinity of thelower rotating fixture 124 in order to show the connection of the bundlealignment assembly 200 to the fuel prep machine 110; FIGS. 5 and 6 arepartial perspective views of the system 1000 to show the attachment ofthe upper mount block 208 to the upper rotating fixture 122.

Referring to FIGS. 4-6, in order to mount the bundle alignment assembly200, an upper mounting bracket 218 and a lower mounting 216 areinstalled on the upper and lower rotating fixtures 122 and 124. Thesewill capture the mating surfaces of the bundle alignment assembly 200.As shown best in FIG. 4, a lower mounting bracket 216 is attached to thelower rotating fixture 124. The lower mounting bracket 216 is configuredto receive an alignment pin 212 which is connected to the bottom of themounting frame 205 of the bundle alignment assembly 200.

The upper mounting bracket 218 is attached to the upper rotating fixture122. Each upper mounting bracket 218 includes a feature which has athreaded cavity 217 therein. The brackets 218 are adapted to receivespring loaded pins 219 which screw therein to connect the upper mountblocks 208 at the upper end of the bundle alignment assembly 200 to theupper mounting brackets 218 of the upper rotating fixture 122. As bestshown in FIG. 6, this secures the bundle alignment assembly 200 to thecarriage 120 of the fuel prep machine 110, with the spring loaded pins219 inserted into the threaded cavities 217 of the upper mountingbrackets 218.

Of note, FIG. 5 provides a clearer view of the internal arrangement offuel rods, comprising full-length fuel rods 155 and part-length fuelrods 160, and water rods 170 within fuel bundle 150. For purposes ofclarity, a number of full and part-length rods 155, 160 have beenremoved so that the water rods 170 and other part-length rods 160 can beseen. Also illustrated are the upper end plugs 165 on the part-lengthfuel rods 160. Further, the fuel spacer 180 with its individual cellsmay be seen in clearer detail.

Accordingly, the bundle alignment assembly 200 is lowered into positionvia its bail 202 so that the lower alignment pins 212 are guided intothe lower mounting brackets 216. The upper mounting blocks 208 are thenpositioned onto the upper mounting brackets 218 and the spring loadedpins 219 are engaged in the upper mounting brackets 218 to secure thebundle alignment assembly 200 into place.

FIG. 7A is a perspective view of an alignment station 210 showingalignment blade bundles 220 in a neutral or disengaged position. Eachalignment station 210 includes a plurality of blade bundles 220. Asshown in FIG. 7A (as well as in FIG. 3A), three (3) alignment bladebundles 220A, 220B and 220C are mounted on a generally C-shaped supportplate 206. Each blade bundle 220 includes a plurality of stainless steelblades 222. However, blades 222 can be formed of other metals, metalalloys or materials having high thermal resistance properties and/orhigh coefficients of thermal conductivity, such as inconel, hightemperature polymers (plastics) and ceramics.

Some of the individual blades 222 are shorter (shown as 222′) thanothers in a given blade bundle 220 so as to create a grid 230 around aportion of the fuel bundle 220 (in this example, half of bundle 150)when the blade bundles 220 are rotated into an engaged position. In FIG.7A, the individual blade bundles 220 are shown in a neutral ordisengaged position. They are movable into an engaged position bycorresponding activation handles 226.

FIG. 7B is a perspective view of the alignment station 210 showing theblade bundles 220 in an engaged position. As shown in FIG. 7B, the bladebundles 220A, 220B and 220C can be rotated into the fuel bundle 150 byactuating the activation handle 226. A hook used on the standardhandling pole is used to actuate the activation handles 226 sequentiallyso as to first rotate the blade bundle 220B, then bundles 220A and 220Cinto the fuel bundle 150.

FIG. 7C is a top view of the alignment station 210 with the bladebundles 220 in an engaged position to illustrate the grid 230 that iscreated for alignment of fuel rods 155/160 and water rods 170 within thefuel bundle 150. FIG. 7C also better illustrates the use of shorterblades 222′ to form grid 230. Alignment blade bundle 220B is rotatablein a first plane, and the other two blade bundles 220A and 220 C arerotated in a second plane above blade bundle 220B so as to form the grid230 around groups of fuel rods 155, 160 and water rods 170. The top viewof FIG. 7C shows how the grid 230 is created with an interior centerspace to provide an opening for the water rods 170. This grid 230 in theexample of FIG. 7C thus aligns approximately half the fuel rods 155/160in fuel bundle 150, which for an example 10×10 fuel matrix are forty-six(46) fuel rods and one (1) water rod. Half of the fuel rods 155/160 withone water rod 170 in bundle 150 are aligned at a time due to toleranceconstraints of the FPM 110. The bundle 150 can simply be rotated withincarriage 120 to permit rods 155/160/170 in the other half of the fuelbundle 150 to be aligned. Of note, the bundle 150 is straightened oncethe blade bundles 220A-C are inserted from one side. Selected fuel rods155, 160 on the other side of the bundle 150 may still have bow ortwist, but the overall bundle 150 profile will be straight in the axialdirection.

For each alignment station 210, the protective grid 230 formed by thealignment blade bundles 220 vertically aligns the fuel rods 155/160 andwater rods 170 above each of the fuel spacers 180 in the bundle 150, asshown in FIG. 1 for example. Of course, alignment stations 210 can belocated below the spacers 180 so that the grid 230 formed by bladebundles 220 vertically aligns the fuel rods 155/160 and water rods 170below each of the fuel spacers 180. If desired, alignment stations 210can be attached just above and below spacers 180 to form the grids 230that align the fuel rods 155/160 and water rods 170 above and below eachof the fuel spacers 180 in the bundle 150.

In an alternative construction, the blade bundles 220 can be rotatedhorizontally to an engaged position such that individual blades 222rotate independent of one another. In this embodiment, selected blades222 may be removed from selected blade bundles 220 to align a particularportion of fuel rods 155/160 in the bundle 150. Different combinationsof blades 222 in each of the blade bundles 220 of an alignment station210 can thus be rotatable to align one or more of a half-section of thebundle 150, a quarter-section of the bundle 150 and an eighth section ofthe bundle 150, for example.

It would be evident to one skilled in the art to include additionalblades 222 with varying or different lengths to accommodate differentfuel rod matrix configurations other than 10×10, such as fuel bundleshaving 9×9 fuel rod matrices or larger fuel bundles such as thedeveloping 17×17 fuel rod groups for pressurized water reactors (PWRs).

FIG. 8A is a perspective view of an alignment blade bundle 220 and FIG.8B is an exploded view of FIG. 8A illustrating the constituent parts ofthe alignment blade bundle 220. Referring to FIGS. 8A and 8B, analignment blade bundle 220 (each of the three alignment blade bundleshave similar parts) includes a base plate 228 which has two side plates232 connected thereto via a plurality of fasteners 234 such as thescrews which are secured within threaded bores 235. The activationhandle 226 is connected to one side of shaft 238 so as to be inrotational engagement with a shaft 238. The shaft 238 extends through abearing/washer assembly shown generally at 239 and through a pair ofpivot blocks 240.

The blades 222 are attached to a blade holder 236 which is affixed tothe top of the pivot blocks 240 via a series of fasteners 241 receivedin corresponding threaded bores 242 in the pivot blocks 240. Each bladebundle 220 also includes a fixed stainless steel blade 237 attached toblade holder 236. The purpose of fixed blade 237 is to provide a rigidpoint to begin fuel rod alignment. A limit stop 243 is provided beneaththe blade holder 236 so as to limit rotational travel of the blades 222to no more than 90 degrees from vertical.

The blade bundle 220 is fixedly secured to the support plate 206 with aspring stop bolt 244 which compresses a spring 246 as it is tightenedinto a threaded bore 248 of the base plate 228. This allows a bladebundle 220 to be quickly removed from and/or reattached to support plate206. An inspection tooling lug 250 is also attached to the base plate228 via suitable fasteners 252 to permit an inspection tooling pole (notshown) to be attached thereon.

FIG. 9 is a partial perspective view of the system 1000 illustrating therod guide block 300 placed over the fuel bundle 150. Referring to FIG.9, the fuel rod guide block 300 has a bail 302 which is attached to astandard handling pole 304 to be lowered down into the spent fuel pooland place just below the upper end plugs of the full length fuel rods155 and the tops of the water rods 170 at the top end of bundle 150. Aspreviously indicated, in the event that the irradiated fuel bundle 150exhibits no twist or bow, only the rod guide block 300 need to beinstalled on top of the bundle 150 above the uppermost spacer 180A.

The fuel rod guide block 300 when in place protects the uppermost spacer180A from damage as fuel rods are inserted therein and also provides analigned lead-in to initially start a replacement fuel rod (full-lengthfuel rod 155 or part-length rod 160) into the fuel bundle 150 with thedesired proper alignment. Thus, the rod guide block 300 acts as both ashield (physically protecting spacer 180A) and a visual aid to show ahandler where a fuel rod needs to be inserted into the fuel bundle 150by providing a clear visual indication due to the structure andarrangement of an upper plate 305 of fuel rod guide block 300.Accordingly, less experienced handlers can perform fuel rod removal andinsertion procedures without requiring the skill and experience of theseasoned handler, since the structure of the fuel rod guide block 300helps to properly and perfectly align each of the fuel rods 155/160 ofthe fuel bundle 150 in the vertical direction.

FIG. 10 is an exploded view of the fuel rod guide block 300 toillustrate constituent parts in more detail. As previously described,the fuel rod guide block 300 is lowered onto the fuel bundle 150 via astandard handling pole 304. In an example, this can be a handling polewith a ½″-13 threaded stud that located on the lowest end of the pole304, that's used to lower the guide block 300 over the fuel bundle 150.The threaded stud is received in the threaded bore 303 in bail 302 ofthe fuel rod guide block 300.

The fuel rod guide block 300 further includes an upper plate 305, alower plate 306, and a plurality of stainless steel vertical tubes 308dimensioned so as to be able to receive a replacement fuel rod 155, 160or a rod grapple tool 400 there through. A pair of side plates 310attach to the upper plate 305 and lower plate 306 so as to secure thetubes 308, upper plate 305 and lower plate 306 together. The side plates310 include a plurality of holes 319 to facilitate decontamination andcleaning of tubes 308 within the guide block 300. As shown in FIG. 10,each of the upper plate 305 and the lower plate 306 have a plurality ofthreaded bores 313 which are configured to receive a plurality offasteners 314 to attach the side plates 310 to the side surfaces of theupper and lower plates 305, 306.

As the example fuel bundle 150 has a 10×10 fuel rod matrix, 92 tubes 308are employed (a space is provided in the center for the water rods 170),and each of the top and bottom plates 305 and 306 have 92 fuel rodopenings 316 for fuel rods 155/160 or grapple tool 400 passage. Openings316 align with the tubes 308 as shown. The upper plate 305 and lowerplate 306 also include a pair of central openings 318 that align withthe water rods 170 in the fuel bundle 150.

Accordingly, openings 316 and 318 mirror the locations of fuel rods155/160 and water rods 170 in fuel bundle 150 and align with the tubes308. Thus, as the fuel rod guide block 300 is positioned onto and/orover the fuel rods 155/160 and water rods 170 of the fuel bundle 150,the fuel rods 155/160 and water rods 170 are properly realigned,eliminating any bow and/or twist that might be present within the bundle150 (such as in a case where the fuel rod guide block 300 is not usedwith bundle alignment assembly 200).

A bail attachment plate 320 is provided on either side of the tubes 308,between its corresponding side plate 310 and the tubes 308. Each bailattachment plate includes a projection 322 which extends through anopening 324 in its corresponding side plate 310. Each projection 322 hasa centrally threaded bore 326 which is to receive a fastener 328 whichsecures each arm 329 of the bail 302 to its corresponding bailattachment plate 320, i.e., the fasteners 328 are captured by thethreaded bores 326 to secure the bail 302 to the bail attachment plates320.

A bail stop 330 is provided on each outside surface of each side plate310, providing a restricted movement mechanism so as to prevent the bail302 from traveling too far. As shown in FIG. 10, the bail stop 330 issecured to the side plate 310 and bail attachment plate 320 with aplurality of fasteners 332 which are captured in threaded bores 333within the bail attachment plate 320.

FIGS. 11A and 11B are partial cutaway views of the fuel rod guide blockto illustrate the placement of the fuel rod guide block 300 over thefuel bundle 150 and on top of the uppermost space 180A. The fuel rodguide block 300 in FIGS. 11A and 11B is shown with an area where thetubes 308 have been removed to illustrate how the water rods 170interact with the guide block 300. As the fuel rod guide block 300 islowered by the handling pole 304, the fuel rods (full-length fuel rods155 since this is the top of bundle 150) and water rods 170 extendthrough the apertures 316, 318 as the fuel rod guide block 300 islowered down into the bundle 150. Downward travel of the fuel rod guideblock 300 is terminated due to tapers 172 (neck-down features) of thewater rods 170. The openings 318 in the upper plate 305 for the waterrods are also tapered as best shown at 307 in FIG. 11B. Thus, when thetapered openings 318 meet the tapers 172 of the water rods 170, the fuelrod guide block 300 downward travel is halted. Accordingly the taperedsurfaces 172, 307 prevent the fuel rod guide block 300 from travelingany further in the downward direction.

FIG. 12 illustrates a partial perspective view of the system 1000 withthe fuel rod guide block 300 in place on fuel bundle 150. Once the fuelrod guide block 300 is in position, the handling pole 304 is removed byrotating it counter clockwise to remove its stud from the threadedopening 303 in the bail 302. After the handling pole 304 is releasedfrom the fuel rod guide block 300, the handling pole 304 is used to tapthe bail 302 either backwards or forwards. The handling pole 304 is thenstored in its normal ready position hanging from the safety handrail 117of the FPM platform 115, for example. FIG. 12 thus illustrates thesystem with the fuel rod guide block 300 in place.

FIGS. 13-16B describe the rod grapple tool 400 in further detail;reference should be made to these figures for the following discussion.The rod grapple tool 400 is shown generally in FIG. 13 from the vantagepoint of the FPM platform 115 looking down into the spent fuel poolbelow towards the fuel bundle 150, which is secured within the carriage120 attached to the FPM 110. As previously noted, the fuel bundle 150includes a plurality of part-length rods 160. The part-length fuel rods160 may be different heights, known as upper part-length rods and lowerpart-length fuel rods. The rod grapple tool 400 is used to retrieve (orinstall) either the upper part-length fuel rods or the lower part-lengthrods 160 from the fuel bundle 150.

A handler grabs the rod grapple tool 400 by a handle 402 to lower therod grapple tool 400 into the fuel bundle 150, such as through one ofthe tubes 308 in the fuel rod guide block 300. The rod grapple tool 400includes a push-pull handle 404. In an optional variation, the push-pullhandle 404 can include indicator markings (shown generally at 403) thatindicates when the rod grapple tooling is in the fully extended positionand/or when it is in the fully closed position, this part of theoperation will be explained in further detail hereafter.

FIGS. 14A through 14D illustrate constituent parts of the part-lengthrod grapple tool 400 in more detail. As shown in FIGS. 14A and 14B, thepart-length rod grapple tool 400 includes a push-pull handle 404 whichis connected to an activation rod 408 via a plurality of fasteners 409that are received in holes 411 in the push-pull handle 404 to becaptured by threaded bores 410 in the activation rod 408. A top end ofactivation rod 408 is inserted up through a threaded sleeve 405 on whicha threaded acme nut 407 rides, into the push-pull handle 404, where itis secured to the push-pull handle by fasteners 409 such as screws.

As shown in FIGS. 14A and 14B, the activation rod 408 is assembled withDelrin bushings 412, spiral retaining ring 414 and spaced retainingrings 416 which secure the Delrin bushings 412 along the activation rod408. The Delrin bushings 412 keep the activation rod 408 centered in anupper housing 418. The upper housing 418 has the handle 402 at one endand a connector 422 at another end for attaching to a connector 424 of alower housing 430 of the grapple rod tool 400. As the fasteners 409 arenot strong enough to counter the potential rotational torque due tounscrewing the part-length rod 160 from its lower tie plate 40, a keystock 413 is provided in a slot 406 of activation rod 408 to absorb thistorque.

As will be seen in further detail, the lower housing 430 contains anextendable gripper rod 431 (see dotted line to denote within theinterior of lower housing 430 in FIG. 14A) which has a gripper 432attached at a distal end thereon. The gripper rod 431 is attachable tothe activation rod 408 within the connectors 422, 424 of upper and lowerhousings 418, 430, and can be extended via push-pull handle 404 toextend the attached gripper 432 outside of the lower housing 430 so asto retrieve a part-length rod 160.

Referring to FIGS. 14C and 14D, the activation rod 408 has a machinedflat end connector 426 which mates with a corresponding machine flat endconnector 428 of the gripper rod 431 within the connector 424 of thelower housing 430. The machine flats on end connectors 426 and 428 keepthe activation rod 408 and gripper rod 431 from rotating so as to allowthe gripper 432 at the end of the gripper rod 431 to be pulled. Theupper and lower housings 418 and 430 are joined at flat facing surfaces423 and 425 by the use of suitable mechanical fasteners 427. Prior toconnecting these housings 418 and 430 together, the activation rod 408is connected to the gripper rod 431 via the end connectors 426 and 428,as best shown in FIG. 14D. In particular, a threaded screw 429 iscaptured through aligned bores in both end connectors 426 and 428 oftheir respective rods 408, 431.

The connection between activation rod 408 and gripper rod 431 allows thegripper 432 which is attached at the distal end of gripper rod to beextendable from the end of the lower housing 430, and hence retractedwithin lower housing 430. Accordingly, the rod grapple tool 400 has anextended position and a retractable or closed position.

FIGS. 15A and 15B illustrate the extended position of the rod grappletool 400. The extended position is only used when loading or removingthe guide pin 435 from gripper 432, as well as locking the gripper 432of rod grapple tool 400 onto a partial-length rod 160 so as to extractit from the fuel bundle 150.

To extend gripper 432, while a handler holds the handle 402, the handlerrotates the acme threaded nut 407 counter-clockwise until it comes intocontact with the push-pull handle 404. This causes the gripper 432 atthe end of gripper rod 431 to be extended out from the end of lowerhousing 430.

As shown best in FIG. 15B, the protective guide pin 435 is inserted intothe gripper 432. The guide pin 435 has a tapered, generally rounded end437 and includes a mating portion 436 thereon to be captured by theguide pin retrieval tool 500 for removing the guide pin 435 from thegripper 432. Once the rod grapple tool 400 is returned to its retractedposition, the protective guide pin 435 remains in place and abuts theedge of lower housing 430 so as to create a flush, smooth surface 450.The rod grapple tool 400 is then inserted down through the fuel bundle150 and spacers 180 to a position above a part-length rod 160 to beextracted.

FIGS. 16A and 16B illustrate the closed position of the rod grapple tool400. Here the guide pin 435 is shown installed as having a flush surface450 with the end of the lower housing 430, with the gripper rod 431 andits gripper 432 retracted therein. This is the position for insertion ofthe rod grapple tube 400 down through the fuel rod guide block 300 intothe bundle 150. The blunt end 433 of the gripper 432 is thus notexposed. While holding the handle 402, the threaded nut 407 is rotatedclockwise. This will draw the gripper 432 up into the lower housing 430such that the guide pin 435 mates flush with the lower housing 430 atsurface 450.

FIGS. 17A-22 illustrate the structure and function of the guide pinretrieval tool 500 in further detail. Once the rod grapple tool 400 isin position within the bundle 150 between a spacer 180 and a part-lengthrod 160, which is to be extracted, the guide pin 435 needs to be removedfrom the rod grapple tool 400. This is accomplished with the pinretrieval tool 500.

FIG. 17A is a perspective view of guide pin retrieval tool 500, and FIG.17B is an enlarged view of detail A in FIG. 17A. The pin retrieval tool500 is positioned between the top of the part-length rod to be extractedand the fuel spacer 180 above the part-length rod 160. The pin retrievaltool 500 is attached to a handling pole 502, only a portion of which isshown in FIG. 17A. The lower portion of the handling tool 502 may bebent as shown to account for limitations in the access of open space offuel prep machine 110. The pin retrieval tool 500 is attached at the endof the handling pole 502 and includes a horizontal extension 504 towhich is attached a tongue 506.

As shown in the enlarged view of detail A in FIG. 17B, the tongue 506includes a mating aperture 508 for capturing the mating portion 436 ofthe guide pin 435, as best shown in FIG. 20, 21 or 22. Accordingly, thetongue 506 is placed under the tapered end 437 of the guide pin 435 sothat the mating aperture 508 engages with the mating portion 436 onguide pin 435. In an alternate example each of the mating aperture 508and mating portion 436 can include threads thereon for engagement.

The pin retrieval tool 500 also includes a pair of semicircular,serrated edges 510 and 512 which form a plurality of adjacentsemicircular ridges that mate flush against the sides of adjacentfull-length fuel rods 155 and/or part-length fuel rods 160 as the tongue506 is inserted into the side of a fuel bundle 150. These serrated edges510 and 512 help to maintain the pin retrieval tool 500 parallel withthe side of the fuel bundle 150 being serviced. The serrated edges 510and 512 thus help to maintain a proper alignment of the tongue 506against the fuel bundle 150 so that the mating aperture 508 properlyengages with the mating portion 436 on guide pin 435 and the tongue 506without difficulty.

FIG. 18 illustrates different tongue 506 length configurations. Thetongue 506 can be reconfigured for varying lengths to reach part-lengthfuel rods 160 which may require tunneling several rows into the fuelbundle 150, in order to reach the interior part-length rod 160 to beextracted. Three different examples lengths of tongue 506A, 506B and506C are shown in FIG. 18, for example. The pin retrieval tool 500 maybe configured with tongue 506A for removing part-length rod 160 from theoutside row of fuel rods 155/160, with tongue 506B for part-length rodsthat are a few rows into the bundle 150 interior, and with tongue 506Cto reach part-length fuel rods 160 at the very center of the fuel bundle150, around the water rods 170, if found to be located within this areaof the fuel bundle 150.

FIGS. 19-22 illustrate a process for removing the guide pin 435 from therod grapple tool 400 within fuel bundle 150. Initially, the handlingpole 502 lowers the pin retrieval tool 500 in the desired locationwithin the bundle (FIG. 19), located just below the rod grapple tool 400so that the tongue 506 is directly under the guide pin 435. The serratededges 510 and 512 of the pin removal tool 500 abut flush to the sides ofthe fuel rods 155 and/or 160 of the fuel bundle 150 to ensure that thetongue 506 is properly oriented (level) so as to mate with the matingportion of the tongue's mating aperture 508 and mating portion 436 ofthe guide pin 435.

The rod grapple tool 400 is then lowered as shown in FIG. 20 so that theguide pin 435 is received into the mating aperture 508 of tongue 506,and then manipulated to engage the mating portion 436 of the guide pin435 with the mating aperture 508 of the pin removal tool 500 so as tocapture the guide pin 435. FIG. 21 illustrates the guide pin 435 fullycaptured by the pin retrieval tool 500. As shown in FIG. 22, thehandling pole 502 is then moved away from the fuel bundle 150 and storedsuspended from FPM platform 115 with the guide pin 435 thereon. Of note,if the guide pin 435 is needed again, it is retrieved from the pinretrieval tool 500 underwater by the rod grapple tool 400.

FIGS. 23A and 23B illustrate the procedure for attaching the gripper 432of rod grapple tool 400 to an upper end plug 165 of a part-length rod160. As previously described, the part-length rod grapple tool 400 mustbe placed in an extended position in order to remove the guide pin 435.This was shown previously in FIGS. 15A and 15B, in which the handlerwhile holding the handle 402 rotates the threaded nut 407counterclockwise until it comes into contact with the push-pull handle404. This extends the gripper 432 with attached guide pin 435 from theend of the lower housing 430.

Accordingly, once the guide pin 435 has been removed by the pinretrieval tool 500, the gripper 432 in its extended position is placedover the upper end plug 165 of the part-length rod 160. This attachesthe part-length rod 160 to the rod grapple tool 400. As shown in FIG.23A, the part-length rod upper end plug shoulder 167 can damage thespacer 180 when removing the part-length rod 160. However, and aspreviously described with reference to FIG. 16A and 16B, rod grappletool 400 is manipulated to its retracted position, which locks thepart-length rod 160 and the rod grapple tool 400 together, making onelong smooth tube for safe part-length rod 160 extraction. This flushconnection is shown generally by surface 450 in FIG. 23B. Accordingly,potential damage due to exposed upper end plug shoulder 167 has beeneliminated by the rod grapple tool 400. The part-length rod 160 can beremoved without causing damage to any of the spacers 180.

The example embodiments of the present invention being thus described,it will be obvious that the same may be varied in many ways. Forexample, the rod grapple tool 400 has been described a being designedfor a part-length rod 160, with another grapple tool used for thefull-length rods 155 and/or tie rods due to a different upper end plugconfiguration. A different version (shorter in length) of this rodgrapple tool 400 may be used for the removal and/or the replacement oftie rods and full length fuel rods 155 within the fuel bundle 150 Forexample, the full-length rods and tie rods can be configured to have thesame upper end plug design as that of the part-length rods 160; thus arod grapple tool having the same gripper 432 could be used forattachment to the upper end plugs of the full length fuel rods 155 andtie rods for removal from the fuel bundle 150. Such variations are notto be regarded as departure from the spirit and scope of the exemplaryembodiments of the present invention, and all such modifications aswould be obvious to one skilled in the art are intended to be includedwithin the scope of the following claims.

What is claimed is:
 1. A method of removing a part-length fuel rod froma fuel bundle, the fuel bundle residing in a spent fuel pool of anuclear reactor plant, the method comprising: providing a fuel prepmachine in the spent fuel pool, supporting the fuel bundle with the fuelprep machine, providing a rod grapple tool with a gripper on the end ofthe rod grapple tool, attaching a protective, removable guide pin with atapered, rounded-end tip portion to a distal end of the gripper,inserting the rod grapple tool into a top end of the fuel bundle,lowering the rod grapple tool down to a desired elevation of the fuelbundle above a top end of the part-length fuel rod within the fuelbundle, the guide pin preventing the rod grapple tool from damagingcomponents of the fuel bundle as the rod grapple tool is inserted intothe fuel bundle, providing a guide pin retrieval tool, lowering theguide pin retrieval tool along the side of the fuel bundle to thedesired elevation, inserting a first portion of the guide pin retrievaltool into a side of the fuel bundle, mating the first portion of theguide pin retrieval tool with the guide pin, and removing the guide pinfrom the end of the rod grapple tool by securing the guide pin on theend of the guide pin retrieval tool.
 2. The method of claim 1, furthercomprising: mating a second portion of the guide pin retrieval toolagainst fuel rods on an outer side of the fuel bundle, the guide pinretrieval tool including, a handling pole, an extension element having afirst end connected to the handling pole and two sets ofvertically-shaped semicircular ridges at a second end of the extensionelement, the semicircular ridges being the second portion of the guidepin retrieval tool, and a tongue attached to the second end of theextension element, the tongue being the first portion of the guide pinretrieval tool, wherein the two sets of vertically-spaced semicircularridges are configured to accomplish the mating of the guide pinretrieval tool against the fuel rods on the outer side of the fuelbundle.
 3. The method of claim 2, wherein, the guide pin has a matingportion, the tip portion being on a distal end of the mating portion,the tongue having a mating aperture which fits over the tip portion ofthe guide pin to mate with the mating portion of the guide pin forreleasing the guide pin from the rod grapple tool so as to expose thegripper.
 4. The method of claim 2, wherein the two sets ofvertically-spaced semicircular ridges maintain the guide pin retrievaltool parallel with the side of the fuel bundle.
 5. The system of claim3, wherein the two sets of vertically-spaced semicircular ridgesmaintain alignment of the tongue level with the fuel bundle tofacilitate engagement of the mating aperture of the tongue with themating portion of the guide pin.
 6. The system of claim 2, wherein thetongue is located between the two sets of vertically-spaced semicircularridges.
 7. The system of claim 3, wherein the tongue is configured tohave varying lengths to ensure that the tongue is capable of reachingvarying depths within the fuel bundle.
 8. The system of claim 1, thepart-length fuel rod having an upper end plug, wherein the rod grappletool is configured to provide a flush fit between the gripper and theguide pin, and between the gripper and the upper end plug of thepart-length fuel rod.